Color photographs widely prevailing today are making progress increasingly rapidly to a degree that they are readily available at virtually any location due to improvements in the photographic materials themselves and in processing techniques. In color photographic paper for preparing color prints for viewing, particularly, impartation of water resistance to paper supports by coating both sides of each support with a resin and practical applications of photographic materials using high silver chloride emulsions having a high silver chloride content as disclosed in PCT International Publication No. WO87/04534 and processing methods thereof bring about rapid high-level processing.
Parallel to pursuance of such rapid processing, techniques for enhancing the quality of print images to be obtained have also been developed. The image quality of color prints now commercially produced has always been improved with the times. However, the required quality is getting higher.
The quality of color images is determined by many kinds of properties such as gradation reproducibility, color reproducibility, granularity and sharpness. Of these, the sharpness is an important property controlling the depiction of details and three-dimensional appearance of images obtained, and an improvement thereof has been earnestly desired.
In the recent development of color print material techniques, however, an improvement in sharpness is not necessarily sufficient. This is largely caused by the performance of paper supports coated with polyolefin resins which are introduced particularly to obtain easy, rapid processing. Namely, a problem has been encountered in that color images on photographic paper using the water-resistant resin-coated paper as a support are inferior in sharpness to those on photographic paper using the baryta paper which has previously been used as a support for photographic paper. The cause of this problem has been considered to be a small amount of white pigment kneaded in the water-resistant resin layer covering the side of the support on which a light-sensitive emulsion layer is formed, which results in scattering and diffusion of light into the resin layer on exposure to deteriorate the images.
Many attempts have been made to overcome this disadvantage of water-resistant resin-coated paper supports.
Techniques for enhancing the content of white pigments dispersed in polyolefin resins are disclosed, for example, in JP-A-51-6531 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-52-35625, JP-A-55-108658, JP-A-55-113039, JP-A-57-151942, JP-A-3-156439 and JP-A-3-156452. Although these techniques tend to improve sharpness, the improvement is insufficient. Further, it has been revealed that a photographic material comprising a support containing a white pigment in an increased content and a high silver chloride emulsion advantageous for rapid processing applied thereto has the disadvantage of fogging at places where pressure have been applied to the material or at places where the material has been bent.
As techniques for increasing the content of white pigments, JP-A-57-27257 and JP-A-57-49946 disclose methods of coating supports with mixtures of pigments and compositions hardenable with electron beams, followed by irradiation with electron beams to form water-resistant resin layers. However, even the use of these technique was found to promote the above-described problem encountered when the high silver chloride emulsions advantageous for rapid processing are used.
As other means, JP-B-57-53937 (the term "JP-B" as used herein means an "examined Japanese patent publication"), JP-A-50-44818, JP-A-57-64235 and JP-A-59-177542 disclose methods of providing hydrophilic colloidal layers containing white pigments between polyolefin-coated paper supports and light-sensitive silver halide emulsion layers. The use of these means can further increase the content of the pigments in the hydrophilic colloidal layers to improve sharpness. In photographic materials in which these techniques and silver chloride emulsions advantageous for rapid processing were combined with each other, the above-described problem of fogging at pressure-applied or bent places was found to become increasingly significant.
As still other means, JP-A-3-113443 and JP-A-4-67033 disclose methods of providing coloring layers containing solid dispersions of colloidal silver or dyes discolorable with processing between reflective supports and light-sensitive emulsion layers. These means are effective to overcome the above-described disadvantage of the supports. However, it has been found that the problem of fogging at pressure-applied or bent places upon use of the high silver chloride emulsions is not solved yet, and often tends to become more serious.
Accordingly, when the water-resistant resin-coated paper supports advantageous for rapid, easy processing are used in combination with the light-sensitive emulsion layers containing high silver chloride emulsions to form color photographic paper, a technique is needed for enhancing sharpness while solving the handling problems such as development of fogging caused by pressure.